Chapter 10 Interfaces
UAG5100 User’s Guide
146
When the bridge receives a packet, the bridge records the source MAC address and the port on
which it was received in a table. It also looks up the destination MAC address in the table. If the
bridge knows on which port the destination MAC address is located, it sends the packet to that port.
If the destination MAC address is not in the table, the bridge broadcasts the packet on every port
(except the one on which it was received).
In the example above, computer A sends a packet to computer B. Bridge X records the source
address 0A:0A:0A:0A:0A:0A and port 2 in the table. It also looks up 0B:0B:0B:0B:0B:0B in the
table. There is no entry yet, so the bridge broadcasts the packet on ports 1, 3, and 4.
If computer B responds to computer A, bridge X records the source address 0B:0B:0B:0B:0B:0B
and port 4 in the table. It also looks up 0A:0A:0A:0A:0A:0A in the table and sends the packet to
port 2 accordingly.
Bridge Interface Overview
A bridge interface creates a software bridge between the members of the bridge interface. It also
becomes the UAG’s interface for the resulting network.
This UAG can bridge traffic between some interfaces while it routes traffic for other interfaces. The
bridge interfaces also support more functions, like interface bandwidth parameters, DHCP settings,
and connectivity check. To use the whole UAG as a transparent bridge, add all of the UAG’s
interfaces to a bridge interface.
A bridge interface may consist of the following members:
• Zero or one VLAN interfaces (and any associated virtual VLAN interfaces)
• Any number of Ethernet interfaces (and any associated virtual Ethernet interfaces)
When you create a bridge interface, the UAG removes the members’ entries from the routing table
and adds the bridge interface’s entries to the routing table. For example, this table shows the
routing table before and after you create bridge interface br0 (250.250.250.0/23) between lan1
and vlan1.
Table 60
Example: Bridge Table After Computer A Sends a Packet to Computer B
MAC ADDRESS
PORT
0A:0A:0A:0A:0A:0A
2
Table 61
Example: Bridge Table After Computer B Responds to Computer A
MAC ADDRESS
PORT
0A:0A:0A:0A:0A:0A
2
0B:0B:0B:0B:0B:0B
4
Table 62
Example: Routing Table Before and After Bridge Interface br0 Is Created
IP ADDRESS(ES)
DESTINATION
IP ADDRESS(ES)
DESTINATION
210.210.210.0/24
lan1
221.221.221.0/24
vlan0
210.211.1.0/24
lan1:1
230.230.230.192/26
wan1
221.221.221.0/24
vlan0
250.250.250.0/23
br0
222.222.222.0/24
vlan1
230.230.230.192/26
wan1
